Electron

Electron, a negatively charged elementary (i.e., not decomposable into simpler) particle. The mass of the electron m = 9.03 × 10^-28 g and charge e = 4.77 × 10^-10 absolute electrostatic units. For very many processes, what is essential is not the absolute value of the mass and charge of the particle, but the ratio of charge to mass, e/m, which for the electron equals 5.28 × 10¹⁷ absolute electrostatic units, or 1.76 × 10⁷ absolute electromagnetic units. The value of e/m for the electron was first determined by Thomson in 1894. The simplest source of electrons is a heated metal surface. From 1 cm² of tungsten surface at t° = 2000°, 6 × 10¹⁵ electrons are emitted per second. The electron possesses a magnetic moment equal to 0.917 × 10^-20 absolute electromagnetic units, as well as a moment of momentum equal to 0.521 × 10^-27 absolute units.